Glossary
Short definitions of the terms these guides use, with a link to where each is
explained. Yano’s command line, configuration, and APIs say app chain where
the guides say app ledger; identifiers such as yano.app-chain.* and
/api/v1/app-chain/ keep their names.
Actor. A person or organization that signs a business decision, such as an approval, with its own key. The signature travels inside the message body. Actors are separate from members. See Keys and trust.
Admission. The check a member runs before it accepts a message into its pending pool. A refusal answers HTTP 400 and keeps the message out of blocks; acceptance answers 202, which is not finality.
Anchor. A certified state root published to Cardano, either in transaction metadata or in a script-controlled output whose inline datum carries the ledger’s identity. Optional; finality never waits for it. See Cardano anchoring.
Anchor leader. The node with anchoring enabled that builds, pays for, and submits anchor transactions. It is fixed and does not rotate. In script mode it needs a threshold of member co-signatures.
App ledger. An application-specific, replicated ledger that a group of organizations runs together. The tooling calls it an app chain. See What is an app ledger?
Binding. A declarative event binding: when one component emits an event, check conditions and build a command for another component. Bindings run identically on every member. Experimental. See Declarative bindings.
Block. An ordered batch of messages, with the state root after applying them, a hash link to the previous block, and a finality certificate. The block hash covers the header; messages are bound through the messages root.
Capability. An entry in the release catalog, such as state:kv-registry or
executor:kafka, with an availability: BUNDLED, FIRST_PARTY_OPTIONAL,
REFERENCE, or EXPERIMENTAL. See the capability catalog.
Capability manifest. The capabilityManifest in a ledger’s status: discovery
data describing its components, workflows, and proof subjects. Not a trust root.
See Chain identity.
Catch-up. How a member that fell behind fetches missed blocks from a peer and verifies each one, including its certificate and state root. See Restart, catch-up and snapshots.
Chain id. The identifier of one app ledger, chain-id in configuration. One
node can host several ledgers.
Commitment profile. The authenticated-state structure, chosen at genesis:
mpf-blake2b256-v1 (MPF) or jmt-blake2b256-v1 (JMT). Only MPF proofs can be
checked on Cardano. See Chain identity.
Composite. One state machine that hosts several components under one state root, applying them in a committed order within each block.
Consensus context. A digest in every block header that binds the chain id, genesis id, height, quorum, member keys, and consensus profiles. Every vote signs it.
Effect. An immutable record that a transition emits to authorize external work, such as a webhook call or a Kafka message. An executor performs it after finality. See Effects.
Executor. The node-local component that performs finalized effects. It runs outside consensus and is off by default.
Fault bound. f, the number of members allowed to be dishonest, set as
consensus.max-byzantine-members (default 0). The threshold t of n members
must satisfy 2t − n > f and t ≤ n − f. See Keys and trust.
Finality certificate. The COMMIT signatures of a threshold of distinct members on one block. A block with a valid certificate is final, and there is no rollback below finality. See Consensus and finality.
Format fingerprint. A hash of the commitment profile’s exact commitment and
proof format, state.format-fingerprint. Fixed at genesis.
Genesis id. 32 bytes, state.genesis-id, that name one generation of a
ledger. Never regenerate the genesis id of a ledger whose data you keep.
Leader. The member that proposes the block for a height and view. With a
fixed sequencer, a configured member leads view 0; with rotating, the view-0
leader is derived from the consensus context and the parent block hash. After a
certified timeout, the next member in order leads.
Member. A node that takes part in a ledger, identified by an Ed25519 public key. Members sign the envelopes of messages they accept, re-execute and vote on every block, and each hold the full state. A ledger has at most 32 members.
Membership epoch. The member set and threshold in force from a given height. With governed membership, changes are finalized ledger transactions, and every check uses the membership at that height.
Message. An envelope with a topic and an opaque body, signed by the member that accepted it. Its message id is derived from its content. Only the state machine interprets the body.
Observation. External information that enters the ledger as certified
input: stable Cardano facts on reserved ~l1/ topics, which every member
re-derives from its own Cardano view, or generic observations certified under a
shared policy (preview). See External observations.
Organization. A governed record that groups actors, so a policy can require approvals from distinct organizations.
PreparedQC. A threshold of PREPARE votes for one block in one view. Members persist it and then sign COMMIT; a later leader must carry it forward.
Preset. A packaged choice made when a ledger is created, such as
machines.composite.preset (default evidence-v1-gated) or a Cardano History
preset (default params-only-v1).
Profile. For a composite, the canonical description of its components, order, routes, versions, and quotas, committed at height 1. It changes only through profile governance.
Proof subject. A typed descriptor, such as finalized-message-v1, that turns
an application identity (a message id, an account, a key) into the canonical
state key and evaluates declared claims on the proven value. See
State and proofs.
Read index. A node-local, rebuildable index derived from finalized blocks,
kept in appchain-indexers/. Never authoritative. See
Where data lives.
Recipe. A reviewed starting point that selects the capabilities and configuration for a kind of ledger. See Recipes.
Sink. A component that pushes finalized blocks to an external system, such as a webhook or Kafka, at least once.
Snapshot. A member-signed copy of one ledger’s database, used to restore or onboard a member. Verified before it is opened. See Restart, catch-up and snapshots.
State machine. The deterministic component that interprets message bodies
and writes state. ordered-log is built in; the others are plugins. See
State machines.
State root. The root of the authenticated state after a block. Every member computes it and compares it byte for byte; proofs are checked against it.
Threshold. The number of member signatures a finality certificate needs.
Set it explicitly; the launchers default to a majority, ⌊n/2⌋ + 1.
Topic. A label inside a ledger for routing and filtering messages. Topics
starting with ~ are reserved for the framework.
Trust level. How far a verified result can be trusted:
INTERNAL_CONSISTENCY_ONLY, CALLER_PINNED_ROOT, NODE_CONFIRMED_L1_REFERENCE,
CALLER_PINNED_ANCHOR, or INDEPENDENTLY_VERIFIED_L1_ANCHOR. See
Keys and trust.
View. A numbered attempt to finalize a height. If a round times out, a threshold of members signs timeouts that form a new-view certificate, and the next view begins with the next leader.